Method of fashioning anchorage heads on metal rods

ABSTRACT

A method of forming an anchoring head on a metal rod which comprises holding the rod near its end in a clamp, locating a ring round the projecting free end, and simultaneously compressing the free end and ring.

mte States Pate [151 3,586,743

Thillet Aug. 29, 1972 [54] METHOD OF FASHIONING [56] References Cited gggISIORAGE HEADS ON METAL UNITED STATES PATENTS 1,491,230 4/1924 Gray ..29/522 UX [72] Invent Georges Gremble France 1,615,591 1/1927 Mallory ..29/4705 ux [73] Assignee: B.V.S., Grenoble, France 2,511,920 6/ 1950 Keller et a1 ..29/522 UX [22] Filed: June 9 1969 2,896,981 7/1959 Cooney ..29/522 UX [21] AWL 831,390 FOREIGN PATENTS OR APPLICATIONS 612,324 1 H1948 Great Britain ..52/223 L [30] Forelgn Apphcauon Pnomy Data Primary Examiner-Charlie T. Moon June 18, 1968 France ..155434 Attorney-Cameron, Kerkam & Sutton [52] US. Cl. ..29/452, 29/509, 29/522, [57] ABSTRACT Int Cl 52/223 25 A method of forming an anchoring head on a metal 0 p I q I 5 u u I I d hi h h 1d th ts d [58] Field of Search.....29/522, 452, 509, 526, 470.5; m w c compnses mg 6 md new m a clamp, locating a ring round the projecting free end, and simultaneously compressing the free end and ring.

2 Claims, 16 Drawing Figures PATENTEDAUBZQ I972 3.686, 743

sum 2 OF 2 Fig 76 Fig.- 14

Fig:12

METHOD OF F ASHIONING ANCHORAGE HEADS N METAL RODS This invention relates to a method of fashioning anchorage heads on metal rods.

For many purposes, more particularly for anchoring the metal rods and wires used in prestressed concrete construction work, it is conventional to secure the high-tensile-strength steel wires by means of a knob or the like formed by compression of the wire at each end.

FIGS. 1 and 2 of the accompanying drawings are diagrammatic views showing the conventional process for wires of circular cross-section. A metal wire 1 is retained between jaws 2 of a clamping member so that a free part 3 of the rod extends out of the clamping member. The part 3 is compressed by a compressing device 4 to form a knob or the like 6 (FIG. 2).

For the anchorage to be at least as safe as the wire, the device 4 must be correctly centered; also, the jaw bearing surfaces 5 must be accurately machined to preclude excessive clearance between the wire and the support. Nevertheless, the portion 7 along which the knob 6 is connected to the wire 1 is often likely to rupture.

The invention relates to a low-cost method of producing anchorage heads which are completely reliable for wires of any cross-section.

According to the invention, before the compressing step a metal ring is threaded onto the free part of the rod, the inner bore of the ring being in cross-section equal to or very slightly larger than the rod, ring length being at most equal to the length of the free part of the rod, whereafter the free part of the rod and the ring are compressed simultaneously by means of the compressing device.

The invention will now be described in greater detail with reference to a number of exemplary embodiments shown in the drawings wherein:

FIGS. 1 and 2 are diagrammatic views of the conventional process hereinbefore described, before and after compression, respectively;

FIGS. 3 and 4 are diagrammatic views of the method according to the invention, before and after compression respectively;

FIGS. 5 and 6 show a constructional variant of the ring, before and after compression respectively;

FIGS. 7 and 8 show a second constructional variant of the ring, before and after compression respectively;

FIGS. 9 and 10 show a variant of the method, before and after compression respectively;

FIGS 1 1 and 12 are plan views of two alternative forms of cross-sectional shapes for the rods and the ring:

FIGS 13 -15 are views in longitudinal section of three constructional variants of the ring; and

FIG. 16 diagrammatically shows an improvement provided by the invention.

The underlying idea of the method according to the invention is shown in FIGS 3 and 4 where, as is conventional, a metal rod 1 is retained between jaws 2 of a clamping member having a bearing surface 5 so that a free portion 3 of rod 1 sticks out of the clamping member. A metal ring 8 formed with an inner bore 9 is threaded onto the free part 3. The bore 9 is in diameter slightly larger than the rod 1 and can therefore be threaded thereon with reduced clearance.

The system formed by the ring and the part 3 is compressed by a compression device 4 as is conventional. Because of friction between the ring surfaces and the bearing surfaces of the device 4 and the clamping member, the central portion of the ring expands and the whole forms a knob 9 shown in FIG. 4. The knob 9 formed by the free part of the rod after compression expands to an extent limited by the ring and becomes joined to the rod at an obtuse angle which lessens the risk of shearing as compared with the conventionally fashioned knob 6. Simultaneous compression of the ring and the rod ensures that the two parts of the knob become rigidly joined together. Ring thickness can be chosen to ensure that the knob has the required bearing surface on the anchorage members.

The ring can be devised in various ways to provide further advantages.

FIGS. 5 and 6 show a ring formed on its periphery with two grooves 10, 11 forming reduced-strength zones leading during compression to the formation of two widened parts 12, 13 which improve the anchorage of the rod.

As can be seen in FIGS 7 and 8, the top cross-section of the ring can be reduced, in which event only the top part of the system formed by the rod and the ring is deformed and the rod anchorage knob 9 can be separated from the bearing surface 5.

As FIGS. 9 and 10 show, a ring 8 can be used whose length is slightly less than the length of the free part 3 of the rod. If the compression device 4 is formed with a recess 14, the rod end is upset to form a second knob 15 which provides anchorage to the ring.

If a further junction between the ring and the rod is required in the form of adhesion or brazing, a coating of plastics or adhesive which will be polymerized after compression, or a tube of hard solder coated with flux or cleaning agent which will melt, can be provided between the ring and the wire or rod before compression.

FIG. 11 is an exemplary plan view of a constructional variant of the ring. The ring periphery, the central bore in the ring, and the free portion 3 of the rod, are of polygonal cross-section. This feature helps the rod and ring to stand up to twisting.

FIG. 12 shows another constructional variant of the ring and rod. In some cases, for instance, in the case of stretched bindings wound around a duct, flat metal members are used which have a better contact surface with the duct wall and which can be wound contiguously. To form such flats economically, round rods 3 shown in chain-dotted lines in FIG. 12 are compressed into the cross-sectional shape shown in solid line in FIG. 12. The ring is devised similarly by starting from a ring pierced with a cylindrical bore of a diameter equal to or slightly greater than the diameter of the initial round rod. Such a ring 8, shown in chain-dotted lines in FIG. 12, is compressed laterally at a controlled pressure such that its bore has the same cross-section as the rod 3 after compression. The ring can then be given heat treatment, whereafter the ring outer surface and the bore can be machined to the required shape. The ring is then threaded onto the rod, whereafter the whole is compressed axially according to the invention to form the anchorage. As in the case shown in FIG. 1 1, this anchorage can transmit twisting forces.

H68. 13 15 show various embodiments of the ring base.

Referring to FIG. 13, the ring base 16 in shape resembles a spherical cap and bears on a matching dished portion 17 formed in the bearing surface of the clamping member 2 or anchorage device 22. This feature enables the bar to be centered satisfactorily on the clamping device 2 or anchorage device 22. Of course, the base 16 and the portion 17 could be of any other equivalent shape such as conical or pyramidal.

Referring to FIG. 14, the periphery of the ring base has a screwthreaded portion 18, so that the ring can be screwed, for instance, onto the anchorage device or receive a nut 23 or any other screwthreaded member adapted to increase the bearing surface on the anchorage device 22 or, for instance, enable wire tension to be adjusted.

Referring to FIG. 15, the base is widened to increase the bearing surface and can be formed with bores 19 adapted to receive, for instance, screws securing to the anchorage device.

FIG. 16 shows an improvement according to the invention for limiting the anchorage head cross-section after compression. A die 20 formed with a bore 21 is disposed around the ring 8 before compression and thus limits expansion of the ring 8 during compression and, depending upon the cross-section chosen for the bore 21, enables the anchorage head to be given a maximum cross-section required, for instance, because of the siting of the anchorage.

The invention is not of course limited by details of the embodiments hereinbefore described, such detail being alterable without departing from the scope of the invention. More particularly, the ring can be of any shape other than the shapes described and can be of any crosssection.

What we claim is:

1. In a method for cold forming anchorage heads on a free end of a tensioned high strength metal rod of non-circular cross-section held by a clamp, the steps of mounting a metal ring on the free end of the tensioned rod adjacent the clamp, the ring slidably fitting singly on the rod and extending over substantially the length of the free end of the rod and then simultaneously axially compressing the free end of the rod and the ring against the clamp thereby radially expanding both the ring and the rod to form an anchorage head.

2. Method as described in claim 1 including the step of varying the cross-section of the ring along its length whereby the rod and ring are expanded varying amounts along the length thereof. 

1. In a method for cold forming anchorage heads on a free end of a tensioned high strength metal rod of non-circular cross-section held by a clamp, the steps of mounting a metal ring on the free end of the tensioned rod adjacent the clamp, the ring slidably fitting singly on the rod and extending over substantially the length of the free end of the rod and then simultaneously axially compressing the free end of the rod and the ring against the clamp thereby radially expanding both the ring and the rod to form an anchorage head.
 2. Method as described in claim 1 including the step of varying the cross-section of the ring along its length whereby the rod and ring are expanded varying amounts along the length thereof. 